"Do not worry too much about your difficulties in mathematics, I can assure you that mine are still greater."

"Pure mathematics is, in its way, the poetry of logical ideas."

"Not everything that counts can be counted. Not everything that can be counted counts."

"A man should look for what is, and not for what he thinks should be."

"So far as the theories of mathematics are about reality, they are not certain; so far as they are certain, they are not about reality."

"Once we accept our limits, we go beyond them."

"Since the mathematicians have invaded the theory of relativity, I do not understand it myself any more."

"Only two things are infinite, the universe and human stupidity, and I'm not sure about the former."

"A person who never made a mistake never tried anything new."